Health-related quality-of-life measurement in patients with Parkinson's disease.

Outcome measures are increasingly used to assess the impact of diseases such as Parkinson's disease (PD) from the patient's perspective. These measures, in the form of questionnaires to assess health-related quality of life (HR-QOL), are of 2 main kinds: generic and disease-specific. The former is intended to be relevant to the widest range of health problems; the latter is developed specifically to assess HR-QOL for a specific condition. Possible consequences of PD have been assessed by generic instruments such as the Sickness Impact Profile (SIP), the Nottingham Health Profile (NHP), the Medical Outcomes Study 36-Item Short Form (SF-36) Health Survey and also by disease-specific instruments; in particular, the Parkinson's Disease Quality-of-Life Questionnaire (PDQL) and 39-Item Parkinson's Disease Questionnaire (PDQ-39). This article summarises the criteria whereby such instruments should be evaluated by potential users and describes in more detail the methods of developing and testing such disease-specific instruments for use in PD. There is a range of valid and feasible methods available for taking into account patients' views of PD outcomes. These will become important outcome measures in future clinical trials of treatment regimes.